Fats are concentrated sources of energy, and their addition to the feed rations of cattle and other ruminants has become standard practice. Fats, however, are prone to oxidation, a degradation process that reduces their nutritional value and produces volatile compounds having unpleasant smells and tastes (i.e., rancidity). The rate of oxidation increases with the degree of unsaturation (or the number of carbon-carbon double bonds). During fat oxidation a free radical is formed by the removal of a labile hydrogen atom from a carbon atom adjacent to a double bond. The resultant free radical is susceptible to attack by oxygen to form a free radical peroxide, which then serves as a catalyst of further oxidation. Thus, the oxidative breakdown of fats is autocatalytic, giving rise to a chain reaction and the formation of undesirable breakdown products.
The feeding of oxidized fats to ruminants, and dairy cows in particular, may contribute to the load of free radical in the animal and exacerbate the susceptibility of the animal to oxidative stress. Furthermore, large amounts of (oxidized or non oxidized) unsaturated or unsaturated fats can interfere with the rumen microbial population, block fiber degradation, and microbial growth. Because of the potential negative impact of certain fats, ruminally inert fats have been developed. Inert fats are fatty acids having increased saturation, fatty acids complexed with calcium, or encapsulated fats. Regardless of how they are made inert, however, inert fats are expensive.
Since feed is a major cost in ruminant production, it is desirable to supplement their rations with lower cost non-inert fats, such as vegetable oils, blends of vegetable oils and animal fats, or feed ingredients with a moderate to high content of fat, such as distillers grains. These fats need to be stabilized, however. One way to stabilize and inhibit the oxidation of fat sources used in ruminant diets is to include an antioxidant in the feed ration. One of the most effective antioxidants is ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, sold under the trademark AGRADO®), which is widely used as an antioxidant or preservative in feed supplements. While effective, ethoxyquin is generally more effective as an antioxidant for fish oil and animal fat, but not as effective for controlling oxidation of plant-derived oils. Moreover, dietary antioxidants have traditionally been used only to control the oxidation of fat sources while they are in storage, but not to control the oxidation of the fat source once fed to a ruminant animal. Consequently, new antioxidant formulations that are effective at controlling oxidation of fats and lipids derived from a broad spectrum of fat sources remains an unmet need in the art.